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Booking·Software Engineer·Onsite - System Design / Architecture·Senior

SeniorPrefer not to say
Jul 2026

Summary

System design round at Booking for a software engineering role. The whole session was one big question about logging and telemetry infrastructure, and it went deep fast. Not a bad experience but they really pushed on the operational corners, not just the happy path.

Questions Asked (1)

Q1

Design a logging and telemetry system for a large application platform where many services emit log and metric events, writes are async, and users need real-time query access for debugging and dashboards.

System DesignTechnical Trade-offsData Modeling
Author's notes

This one sprawled in every direction.

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AI HintsAI Generated

Suggested Approach

Start by clarifying requirements and scale, then design a pipeline that decouples ingestion from storage using a message queue. Propose a storage layer optimized for both real-time queries and long-term retention, and discuss trade-offs around consistency, latency, and cost.

Pro tip: Emphasize the importance of backpressure and data durability in async writes, and suggest a tiered storage approach (hot vs. cold) to balance real-time query performance with cost efficiency.

1. Clarify Requirements and Scale

Ask about expected event volume, latency requirements for real-time queries, retention policies, and query patterns (e.g., ad-hoc debugging vs. dashboards).

2. Design Ingestion Pipeline

Propose a scalable ingestion layer using a distributed message queue (e.g., Kafka) to handle async writes, with producers from services and consumers writing to storage.

3. Choose Storage and Indexing

Select a storage solution that supports fast writes and real-time queries, such as a time-series database (e.g., Prometheus for metrics) and a log search engine (e.g., Elasticsearch for logs), possibly with tiered storage.

4. Enable Real-Time Query and Dashboards

Design a query layer that can serve real-time data from hot storage and historical data from cold storage, with caching and pre-aggregation for dashboards.

5. Address Trade-offs and Reliability

Discuss trade-offs: consistency vs. availability, latency vs. cost, and how to handle failures, backpressure, and data retention.

Key Points to Mention

  • Use of Kafka or similar for decoupling and buffering async writes
  • Time-series database for metrics (e.g., Prometheus, InfluxDB) and log search engine for logs (e.g., Elasticsearch, Loki)
  • Tiered storage: hot storage for recent data, cold storage (e.g., S3) for older data
  • Real-time query capabilities: indexing, caching, and pre-aggregation
  • Backpressure handling and data durability guarantees
  • Trade-offs between consistency, latency, and cost

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.